A TiO2-Coated Reflective Layer Enhances the Sensitivity of a CsI:TI Scintillator for X-ray Imaging Sensors

Abstract

Columnar-structured cesium iodide (CsI) scintillators doped with thallium (Tl) are frequently used as x-ray converters in medical and industrial imaging. In this study we investigated the imaging characteristics of CsI:T1 films with various reflective layers aluminum (Al), chromium (Cr), and titanium dioxide (TiO2) powder coated on glass substrates. We used two effusion-cell sources in a thermal evaporator system to fabricate CsI:T1 films on substrates. The scintillators were observed via scanning electron microscopy (SEM), and scintillation characteristics were evaluated on the basis of the emission spectrum, light output, light response to x-ray dose, modulation transfer function (MTF), and x-ray images. Compared to control films without a reflective layer, CsI:T1 films with reflective layers showed better sensitivity and light collection efficiency, and the film with a TiO2 reflective layer showed the best properties.